1. Field of the Invention
The invention relates to pistons for internal combustion engines.
2. Discussion of the Prior Art
A conventional piston for an internal combustion engine comprises a crown, a gudgeon pin bore and a skirt extending all around the piston. The skirt performs no gas sealing function; this is provided by piston rings carried on the piston. Rather, the skirt transmits lateral thrust on the piston produced by a connecting rod during reciprocation to an associated cylinder or liner.
Although the weight of such pistons has, in recent years, been reduced by use of aluminium or aluminium alloys, such pistons are still comparatively heavy and the area of skirt in contact with the cylinder or liner provides a considerable frictional force which must be overcome by the engine, so reducing its power. There have been various proposals for reducing the area of the skirt, but, in general, they have not achieved commercial success because of problems of lubrication and skirt rigidity.